I am somewhat surprised you can comission 8 ships per yard in 3 years. the dutch comissioned their walrus class (4 ships) from 1990 to 1994. (this would have been 1989-1994 if there was not a fire on the lead ship during the construction)
since the construction time of a submarine is a time consuming process (the construction of the walrus class took 9 years) this means your yard requires 8 slibways/docks for these submarines.
in short, I highly doubt you can build submarines in 1-2 years, and I highly doubt you will find any yard (let alone 2) capable of doing so with all these ships at the same time.
in addition, when you do this, you build up a yard (or 2) for this purpose, and then all the equipment gets lost over time because it will not be used for 20+ years. (the netherlands let a 'submarine construction gap' happen and we lost the yard over that, now we have to look to germany or other countries that have the capability still for our new submarines.
I based the number on the Ula class, but since this class is more modern than Ula class... then you are most likely correct.
Ula class stated:
Laid down: unknown (some say 1987 for HNoMS Ula) (But the joint development on the class was from 1972-...)
Launched: 1988 (HNoMS Ula)
Commissioned: 1989 (HNoMS Ula)
Walrus class is much bigger (8 meter+-): 79-85/89-92
So what I can do is change the numbers, that easy. Let us say:
The first ship from both shipyard have 6 year building time
then they follow with first an 4 year build period where the last five have an 3 year build period.
Note that every build group (build period) is of 3 submarines per shipyard, these 2+1 (5)* submarines are build next to each other, this cut the building time down a little, it give an more efficient build method.
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one of the reason I went for one of the Naval shipyard and the the Larger "Warder Advanced shipyard's" (The "Advanced" name was just an gimmick from one of the bosses!).
The Boker Naval shipyard have one of the largest Naval docks with capacity to take in an super-carrier, and it have several small docks. a shipyard often described as an "city" by workers. The Boker Naval shipyard main task is to service all type of naval ships, and build new once. It even have the capability to take in several of Haram's nuclear submarines, But it lack facility to handle nuclear powerplant, for that Haram have an special facility.
The "Warder Advanced shipyard's" however is an quit large shipyard, often doing large build for the Navy, but also very difficult build for the Navy (they even made an full scale copy of one of the 16" guns from a WW2 BB, for a monument, and it is said that, that gun is working!(just a little fun fact)) When Warder is not working for the Navy, they working on sub-sea technology, oil rigs, commercial ships, special cargo ships and one of the sister company's, is working on space technology.